1. Field of the Invention
The present invention relates to systems and methods for digital time interpolation. More particularly, the present invention relates to systems and methods for employing phase-locked loop timing interpolation techniques to provide high timing resolution of when an event signal occurs.
2. Related Art
Many devices depend on measuring the timing of an event signal. Such devices typically use a reference signal to latch the state of an unknown event signal to detect when and if the event signal occurred. The reference signal, as a known reference point, is then interpolated by the event signal. Thus, an estimated time value between the reference signal and the point at which the event signal is latched can be calculated.
Two application areas requiring event timing are laser interferometers and frequency counters.
Laser interferometers require event timing in order to perform displacement measurements. However, conventional displacement measurements of laser interferometers are limited by the resolution of timing measurements of the interference patterns from the measurement and reference receivers. In other words, the displacement measurement resolution is limited by the accuracy of measuring the phase of the interference pattern of a Doppler shifted split frequency laser light at the measurement and reference receivers.
Frequency counters also use interpolation techniques to determine event timing. The interpolator resolution limits the performance of the counter, for example, when time interval measurements are being made on the input signal.
Conventional interpolation techniques are limited in resolution by the smallest possible period reference signal that can be accurately used. Yet, in many instrument applications, the critical measurement is the timing of an event. Thus, there is a need for a device that can accurately increase resolution beyond current limitations on the reference signal period.